In order to force the government not to join a regional free trade pact, thousands of Japanese farmers marched through central Tokyo Wednesday (Oct 26).

Expectation is growing that Prime Minister Yoshihiko Noda, who has said free trade deals are necessary for economic growth, will decide soon to take part in negotiations on the Trans-Pacific Partnership (TPP), a US-led Asia-Pacific trade deal.

The TPP would in principle eliminate all tariffs within the zone, including on farm products, which have largely been excluded from Japan's previous free trade deals.

Joining the free trade initiative would help Japan's auto and high-tech exporters compete in the global market, but would deal a blow to its well-protected farming sector by opening the door to cheaper overseas farm products.

About 4,000 people rallied in Tokyo, holding signs saying "Protect Japan's land and food" and wearing headbands with the words "Absolutely against TPP".

"It is self-evident that we will be facing a collapse of our agriculture,"said Mamoru Ohiraki, a 43-year-old rice farmer at the rally coordinated by the powerful farm lobby Agricultural Cooperative Association, known as JA.

"Beyond even the arguments of trade negotiations, (TPP) will put us at a disadvantage on the security angle too as it will cripple our ability to create self-sufficient food supply."

Japan's agricultural sector, whose output accounts for about 1% of Japan's gross domestic product (GDP), has been protected so far by high tariffs so that farmers, who have substantial political clout, can keep their businesses.

Most Japanese farmers are elderly and work part-time on small plots of land, and experts say the sector faces a grim future without reforms.

Farmers can sway election outcomes due to their clout and because Japan's electoral system favours rural over urban votes.

Noda is expected to decide whether to participate in negotiations for the TPP ahead of an Asia-Pacific Economic Cooperation (APEC) leaders meeting in November.

Despite opposition from farmers and some lawmakers, the government and some ruling Democratic Party executives have started to lay the groundwork for joining the talks.

To help convince resisting lawmakers, the government said last week it plans to strengthen the farming sector by paying subsidies to farmers to sell or lease their land to form larger farms that can withstand foreign competition.

The ruling Democratic Party's policy chief also said this week that depending on how the negotiations go, it would still be possible for Japan to pull out of talks and not join the pact.

Masahiko Yamada, a ruling party lawmaker and a former farm minister who is opposed to Japan joining the talks soon, said if a government forged a decision too quickly, it could deepen a split in the ruling party.

"If the government were to express its participation in the TPP, there are some people in our group, which is cautiously considering the TPP, who say they cannot help but leave the party," he told a news conference.

Japanese businesses, facing a strong yen and high corporate tax rates, are pushing for the government to join the pact. Besides the US, Australia, New Zealand and six other nations are taking part in the TPP talks.

If Japan participates in the TPP, the nation's real GDP would be boosted by JPY2.7 trillion (US$35.5 billion) and nearly half of it would come from increased exports to the US, media reports said, citing the cabinet office.